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排序方式: 共有293条查询结果,搜索用时 15 毫秒
1.
Franca M. Cordero Francesco De Sarlo Alberto Brandi 《Monatshefte für Chemie / Chemical Monthly》2004,40(2):649-669
The review outlines the various different azaheterocycles available from 5-spirocyclopropane isoxazolidines. These compounds can be regarded as versatile direct precursors of tetrahydro-, dihydropyridone and azetidinone derivatives. The current scope and limitations, and the selectivity aspects of the different processes are discussed therein. 相似文献
2.
Giampiero Bettinetti Milena Sorrenti Laura Catenacci Franca Ferrari Silvia Rossi Ilaria Salvadeo Paolo Carraro 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):329-332
Triacetyl α-cyclodextrin, triacetyl β-cyclodextrin and triacetyl γ-cyclodextrin were tested as possible hydrophobic carriers
to prolong the release of hydrophilic teicoplanin (TCP). Physical–chemical characterization of individual components, drug-carrier
physical mixtures at 0.5, 0.67 and 0.75 mass fraction of carrier, and the respective interaction products by kneading or evaporative
crystallization under microwave irradiation was carried out using differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA). In vitro drug release in pH 7.4 phosphate buffer at 37 °C was determined by intrinsic dissolution rate (IDR)
measurements on non disintegrating compressed discs. Solid-state interactions of TCP with triacetyl α-cyclodextrin by evaporative
crystallization and kneading and with triacetyl β-cyclodextrin by evaporative crystallization (probably resulting in carrier
amorphization) were demonstrated. The role of carrier hydrophobicity, carrier mass fraction and preparation method of solid
drug-carrier combinations on solid-state drug-carrier interactions and slowing down of TCP release was assessed. Modulation
of drug release can be achieved using TCP-triacetyl γ-cyclodextrin combinations at 0.5 mass fraction of carrier. 相似文献
3.
Raffaele P. Bonomo Vincenzo Cucinotta Franca D' Allessandro Giuseppe Impellizzeri Giuseppe Maccarrone Enrico Rizzarelli Graziella Vecchio 《Journal of inclusion phenomena and macrocyclic chemistry》1993,15(2):167-180
The functionalized cyclodextrin 6-deoxy-6-[1-(2-amino)ethylamino]--cyclodextrin was synthesized, and an NMR, EPR, pH-metric, and calorimetric investigation was carried out in aqueous solution in order to ascertain its behaviour towards protonation and copper(II) complex formation. The thermodynamic parameters of the ternary complex formation with alanine, phenylalanine and tryptophan enantiomeric pairs were also determined (25° C andI=0.1 mol dm–3). No thermodynamic enantioselectivity was observed in these systems, while a chiral, though poor, discrimination was observed in LEC: c.d. spectra also show enantiomeric stereoselectivity. The results of the present investigation, compared with previously reported results, suggest the occurence of acis-complex trans-complex equilibrium in such systems. 相似文献
4.
Leardini R Nanni D Pareschi P Tundo A Zanardi G 《The Journal of organic chemistry》1997,62(24):8394-8399
A novel cascade radical reaction is described involving aryl isothiocyanates and 2-cyanoaryl radicals. The mechanism entails the formation of an alpha-(arylthio)imidoyl radical, a 5-exo-dig cyclization onto a cyano group, and a final 6-membered ring closure of an iminyl radical. The competitive 5-membered spiro-cyclization of the iminyl, leading to an isomeric product, was only observed in the case of a disubstituted aryl isothiocyanate. The whole process involves a rare example of [3 + 2] radical annulation and allows the one-pot synthesis of tetracondensed nitrogen heterocycles in good yields. 相似文献
5.
The manifold of coupling constants parametrizing a quantum Hamiltonian is equipped with a natural Riemannian metric with an operational distinguishability content. We argue that the singularities of this metric are in correspondence with the quantum phase transitions featured by the corresponding system. This approach provides a universal conceptual framework to study quantum critical phenomena which is differential geometric and information theoretic at the same time. 相似文献
6.
A Cationic Zinc Hydride Cluster Stabilized by an N‐Heterocyclic Carbene: Synthesis,Reactivity, and Hydrosilylation Catalysis 下载免费PDF全文
Dr. Arnab Rit Dr. Alessandro Zanardi Dr. Thomas P. Spaniol Prof. Dr. Laurent Maron Prof. Dr. Jun Okuda 《Angewandte Chemie (International ed. in English)》2014,53(48):13273-13277
The trinuclear cationic zinc hydride cluster [(IMes)3Zn3H4(THF)](BPh4)2 ( 1 ) was obtained either by protonation of the neutral zinc dihydride [(IMes)ZnH2]2 with a Brønsted acid or by addition of the putative zinc dication [(IMes)Zn(THF)]2+. A triply bridged thiophenolato complex 2 was formed upon oxidation of 1 with PhS? SPh. Protonolysis of 1 by methanol or water gave the corresponding trinuclear dicationic derivatives. At ambient temperature, 1 catalyzed the hydrosilylation of aldehydes, ketones, and nitriles. Carbon dioxide was also hydrosilylated under forcing conditions when using (EtO)3SiH, giving silylformate as the main product. 相似文献
7.
Franca Martini 《Annali dell'Universita di Ferrara》1978,24(1):17-24
Riassunto In questo lavoro si generalizza la dualità di Poincaré a spazi topologici localmente omeomorfi con insiemi analitici realin-dimensionali con singolarità isolate; tali spazi non sono in generale orientabili, nè sono muniti di una struttura analitica
globale.
Rispetto ad un analogo risultato diL. Kaup ([6]), il nostro Teorema 2 si dimostra a prescindere dall'esistenza di normalizzazioni topologiche (nel senso di [6]).
Lavoro eseguito come borsista del C.N.R. nell'ambito del G.N.S.A.G.A. 相似文献
Summary In this paper we generalize Poincaré duality to topological spaces locally homeomorphic with real analyticn-dimensional sets with isolated singularities; these spaces are in general neither orientable nor globally analytic. Compared with a similar result ofL. Kaup ([6]), our Theorem 2 is proved without supposing the existence of a topological normalization (in the sense of [6]).
Lavoro eseguito come borsista del C.N.R. nell'ambito del G.N.S.A.G.A. 相似文献
8.
Summary The phosphorus ylide obtained from the reaction between 2-aminobenzo[d]isothiazol-3-one and dimethyl acetylenedicarboxylate in the presence of triphenylphosphine undergoes a smooth intramolecular
Wittig-type reaction to produce, in a one-pot reaction, 3-H-benzo[d]pyrazolo[1,5-b]isothiazole-2,3a-dicarboxylic acid dimethyl ester, a novel functionalized heterocyclic compound. 相似文献
9.
B. ZanfrogniniA. Colina A. HerasC. Zanardi R. SeeberJ. López-Palacios 《Polymer Degradation and Stability》2011,96(12):2112-2119
Poly(3,4-ethylendioxythiophene) films were electropolymerized in aqueous medium without using any surfactant, on glassy carbon electrodes. UV/Vis and Raman spectroelectrochemical techniques were used to analyze the degradation of the polymer film occurring at different pH values. Spectroelectrochemistry has proven to be a very useful analytical tool for this purpose, thanks to its ability to provide information not only about the extent of degradation, but also about mechanistic aspects of the process. From our results we extracted important information about the main factors that play a role in the degradation, in particular about the influence of repetitive doping and de-doping cycles and of photo-induced processes, as a function of the characteristics of the solution, i.e. of pH. 相似文献
10.
Cocchi M Franchini G Manfredini M Marchetti A Pigani L Seeber R Tassi L Ulrici A Vignali M Zanardi C Zannini P 《Annali di chimica》2002,92(3):177-185
A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges--and corresponding counterions--trapped inside the film coating can be reasonably hypothesised. 相似文献